Liver disease is currently the most common cause of non-AIDS morbidity and mortality in developed countries amongst HIV infected people. Indeed, non-alcoholic fatty liver disease (NAFLD) is more prevalent during HIV infection compared to the uninfected population occurring in 30-40% of HIV-infected individuals. Critically, fatty liver disease is becoming an increasingly recognized precursor to non-alcoholic steatohepatitis (NASH), which can further develop into cirrhosis and liver failure. Progression toward NAFLD and steatohepatitis is multifactorial, and includes metabolic changes, cytokine release associated with TLR stimulation and oxidative stress. With regards to HIV infection, the precise drivers and mechanisms of liver disease are not well defined. This proposal will utilize the pathogenic SIV infection of rhesus macaques and in vitro human cell cultures to delineate the early mediators that drive liver disease during SIV/HIV infection. Our previous study assessing livers from SIV-infected and SIV-infected-cART-treated macaques (assessed at necropsy) identified increased levels of bacterial 16s DNA in the livers of both groups. Importantly, an unexpected finding from this study was the enrichment of Mycobacterial 16s DNA in the liver of infected macaques, which we have subsequently identified as Mycobacteria smegmatis, a commensal or potentially opportunistic pathogen. These data, as well as published findings, have led to the hypothesis that translocation of bacteria and bacterial products to the liver (including Mycobacteria-associated dysbiosis) are key mediators of liver inflammation during cART-treated HIV/SIV-infection and can initiate the early events that trigger fatty liver disease. This hypothesis will be tested through three specific aims the first two Aims assess immune and microbiome changes within the liver, lymph node and blood in SIV-infected-cART-treated macaques. Aim 3 will evaluate the mechanisms underlying changes observed in human macrophages or hepatocytes utilizing in vitro experiments following exposure to HIV, cART and bacteria/PAMPs. Our goal is to delineate the role of bacterial translocation and microbiome dysbiosis in HIV/SIV-associated liver inflammation, with particular focus on mycobacteria. To undertake these aims, this study will be led by Dr. Sodora, who has 18 years of experience evaluating immune inflammation during HIV/SIV disease including previous studies assessing liver inflammation during SIV-infection and cART-treatment. In addition, the team consists of Drs. Burwitz, Sacha and Smedley at the Oregon National Primate Research Center who have the necessary expertise to successfully undertake the outlined experiments. Collectively, these approaches will allow us to undertake a mechanistic assessment of the precise contributions of HIV/SIV virus, cART drugs and gut-derived microbes in liver inflammation as well as identify potential synergistic effects of these mediators when combined in a macaque or in vitro. Our long-term goal is to identify an immune therapeutic strategy to reduce incidence and/or severity of liver disease in HIV-infected and cART-treated individuals.